This invention is directed toward a method for recharging electrochemical battery systems. More precisely, a method suitable for use in systems characterized by high depth discharge batteries used in systems requiring long life and experiencing frequent recharging.
In particular demand for such battery systems are traction application systems such as electric vehicles. Such systems are typified by deep discharges and, in order to meet typical customer requirements, will require a substantially long useful life experiencing frequent, rapid recharges. Conventional gas recombinant lead acid batteries have been improved upon structurally with the advent of "starved electrolyte" designs to forestall material shedding and sulfating at the bottom of the plates thereby extending life cycles to a certain degree. However, structural changes have limited ability to address other factors contributing to degradation of a battery's capacity over numerous cycles.
It is well recognized that the cycle life of gas recombinant lead-acid batteries is very dependant upon the charge voltage and particularly so as the battery approaches a full charge. However, conventional charging regimes contribute little to extending the life of gas recombinant batteries. In fact, gas recombinant lead-acid batteries recharged conventionally will experience degradation attributable to drying out, plate surface polarization and grid corrosion thereby lessening the capacity on each subsequent cycle. Additionally, mere conservative voltage and current control will yield extended charge times while too aggressive a voltage and current control will result in excess gas generation and accelerated capacity degradation.